Hietaniemi Beach is the correct name of the place. But apparently people can't stop disagreeing with me so I guess I must do it.

The sea extends beyond the maritime boundaries so your excuse for reverting isn't valid. There is no official language of the sea.

I cannot gather any on-the-ground evidence for anything because I live in the middle of nowhere in the countryside with my parents and I don't have a car. So if something is further than a few kilometres away, I have to rely on Google searches.

According to Wikipedia (https://en.wikipedia.org/wiki/Kanta-H%C3%A4me): "sometimes referred to by the obsolete Tavastia Proper". Google also says that I'm currently in Tavastia Proper.

As a native English speaker living here, I think every place should have an English name, no matter if it's obsolete.

TL;DR according to both Wikipedia and Google, Tavastia Proper is a valid name for it.

Ok, I won't add :en tags anymore if you don't want it. I just thought it would be easier for software and screen readers on English language devices to read the name if it's written just a little bit differently. Plus the :en tags aren't even visible on the map by default so I thought they're harmless. I guess names of places should be made official by the local authorities before being included in any maps (I don't know if it's even legal to have non-Finnish or Swedish place names in Finland)